Approaching the External Quantum Efficiency Limit in 2D Photovoltaic Devices

Area of Science:

• Materials Science
• Nanotechnology
• Renewable Energy

Background:

• 2D transition metal dichalcogenides (TMDs) show promise for ultrathin photovoltaic devices.
• Current 2D photovoltaic devices struggle with low photocarrier separation and collection, limiting external quantum efficiency (EQE) and power conversion efficiency (PCE) below 50% and 3% respectively.

Purpose of the Study:

• To develop high-performance 2D photovoltaic devices by addressing limitations in photocarrier separation and collection.
• To demonstrate a universal strategy for enhancing the performance of 2D photovoltaic devices based on TMDs.

Main Methods:

• Fabrication of 2D photovoltaic devices using tungsten disulfide (WS2) with a focus on creating a defect-free interface and a recombination-free channel.
• Utilizing van der Waals metal contacts to eliminate interface defects and Fermi-level pinning.
• Achieving a fully depleted channel to prevent photocarrier recombination.

Main Results:

• Demonstrated 2D WS2 photovoltaic devices with a high EQE of 92% and PCE of 5.0%.
• The strategy proved effective for other TMDs, with MoSe2 achieving 92% EQE and WSe2 achieving 94% EQE.
• The developed devices exhibited intrinsic photocarrier separation and collection with high efficiency.

Conclusions:

• A universal strategy for fabricating high-performance 2D photovoltaic devices using TMDs has been proposed.
• The near-ideal EQE achieved suggests significant potential for PCE to approach the Shockley-Queisser limit.
• This approach overcomes key challenges in 2D material-based solar cells, paving the way for next-generation photovoltaics.